1. Field of the Invention
The present invention relates to a tissue culture device, and more particularly, concerns a multiwell tissue culture assembly for in vitro cultivation of cells in growth media, with features to reduce the media evaporation during use.
2. Description of the Prior Art
Tissue culture assemblies, frequently referred to as tissue culture plates, are commonly used for in vitro cultivation of cells particularly for experimental purposes. Multiwell tissue culture plates have been used for these purposes, and include six, twelve, twenty-four, forty-eight and ninety-six wells. Such multiwell tissue culture plates are convenient for the investigator in order to conduct tests for the separation of individual cell cultures while maintaining the cultures in close proximity (all in one plate with a single lid) for performance of related tests or assays on all the cultures.
Presently known and available lids for covering multiwell tissue culture plates have been designed to serve at least three purposes: (1) maintenance of sterility of the contents within the wells, (2) elimination of well-to-well cross contamination due to vapor condensation on the lid undersurfaces, and (3) maintenance of adequate atmospheric ventilation or air exchange between well interiors and the external environment. While the first two of the aforementioned purposes have been served well by current multiwell tissue culture plate lids, the last mentioned feature has not been adequately provided. Specifically, currently available lids for multiwell tissue culture plates permit too much air to flow to the wells from the external environment. In a larger multiwell tissue culture plate, such air exchange generally causes no problems with respect to the media and cell cultures in the interior wells. However, those wells around the periphery or the corners of the tissue culture plate are disturbed by excess airflow from the external environment. Excess air causes the evaporation of cell culture media, resulting in a concentration of media constituents. As a result, in the peripheral and corner wells, osmolarity of the media is not in balance with cellular protoplasm. Consequently, cell growth is retarded in those wells where media evaporation has occurred due to this excessive air exchange. Media must either be replenished more frequently to compensate for evaporation, or the peripheral or corner wells are not used for the cell culturing procedures.
Multiwell tissue culture assemblies are exemplified in U.S. Pat. Nos. 4,349,632; 4,038,149; 4,012,288; 4,010,078; 3,597,326 and 3,107,204. Another culture vessel is exemplified in U.S. Pat. No. 4,358,908. None of the inventions described in the above-listed patents overcomes the problem of media evaporation due to excessive air exchange between the wells and the external environment.
Accordingly, there is still a need for a multiwell tissue culture assembly which is capable of reducing the air flowing to the wells, so as to cause a reduction in evaporation of media in the wells, while maintaining sufficient air flow to allow equilibration between culture media in the wells and atmospheric conditions external to the multiwell tissue culture assembly. The present invention is directed to such a multiwell tissue culture assembly which solves the above-described problems.